// Copyright 2018 The OPA Authors.  All rights reserved.
// Use of this source code is governed by an Apache2
// license that can be found in the LICENSE file.

// Package bundle implements bundle downloading.
package bundle

import (
	"context"
	"fmt"
	"reflect"
	"sync"

	"github.com/open-policy-agent/opa/ast"
	"github.com/open-policy-agent/opa/bundle"
	"github.com/open-policy-agent/opa/download"
	"github.com/open-policy-agent/opa/plugins"
	"github.com/open-policy-agent/opa/storage"
	"github.com/open-policy-agent/opa/util"
	"github.com/sirupsen/logrus"
)

// Plugin implements bundle activation.
type Plugin struct {
	config     Config
	manager    *plugins.Manager             // plugin manager for storage and service clients
	status     *Status                      // current plugin status
	etag       string                       // etag on last successful activation
	listeners  map[interface{}]func(Status) // listeners to send status updates to
	downloader *download.Downloader
	mtx        sync.Mutex
}

// New returns a new Plugin with the given config.
func New(parsedConfig *Config, manager *plugins.Manager) *Plugin {
	p := &Plugin{
		manager: manager,
		config:  *parsedConfig,
		status: &Status{
			Name: parsedConfig.Name,
		},
	}
	p.initDownloader()
	return p
}

// Name identifies the plugin on manager.
const Name = "bundle"

// Lookup returns the bundle plugin registered with the manager.
func Lookup(manager *plugins.Manager) *Plugin {
	if p := manager.Plugin(Name); p != nil {
		return p.(*Plugin)
	}
	return nil
}

// Start runs the plugin. The plugin will periodically try to download bundles
// from the configured service. When a new bundle is downloaded, the data and
// policies are extracted and inserted into storage.
func (p *Plugin) Start(ctx context.Context) error {
	p.logInfo("Starting bundle downloader.")
	p.mtx.Lock()
	defer p.mtx.Unlock()
	p.downloader.Start(ctx)
	return nil
}

// Stop stops the plugin.
func (p *Plugin) Stop(ctx context.Context) {
	p.logInfo("Stopping bundle downloader.")
	p.mtx.Lock()
	defer p.mtx.Unlock()
	p.downloader.Stop(ctx)
}

// Reconfigure notifies the plugin that it's configuration has changed.
func (p *Plugin) Reconfigure(ctx context.Context, config interface{}) {
	p.mtx.Lock()
	defer p.mtx.Unlock()

	newConfig := config.(*Config)
	if reflect.DeepEqual(p.config, *newConfig) {
		p.logDebug("Bundle downloader configuration unchanged.")
		return
	}

	p.logInfo("Bundle downloader configuration changed. Restarting bundle downloader.")
	p.config = *config.(*Config)
	p.downloader.Stop(ctx)
	p.initDownloader()
	p.downloader.Start(ctx)
}

// Register a listener to receive status updates. The name must be comparable.
func (p *Plugin) Register(name interface{}, listener func(Status)) {
	p.mtx.Lock()
	defer p.mtx.Unlock()

	if p.listeners == nil {
		p.listeners = map[interface{}]func(Status){}
	}

	p.listeners[name] = listener
}

// Unregister a listener to stop receiving status updates.
func (p *Plugin) Unregister(name interface{}) {
	p.mtx.Lock()
	defer p.mtx.Unlock()

	delete(p.listeners, name)
}

func (p *Plugin) initDownloader() {
	client := p.manager.Client(p.config.Service)
	path := fmt.Sprintf("/bundles/%v", p.config.Name)
	p.downloader = download.New(p.config.Config, client, path).WithCallback(p.oneShot)
}

func (p *Plugin) oneShot(ctx context.Context, u download.Update) {
	p.mtx.Lock()
	defer p.mtx.Unlock()

	p.process(ctx, u)
	status := *p.status

	for _, listener := range p.listeners {
		listener(status)
	}
}

func (p *Plugin) process(ctx context.Context, u download.Update) {

	if u.Error != nil {
		p.logError("Bundle download failed: %v", u.Error)
		p.status.SetError(u.Error)
		return
	}

	if u.Bundle != nil {
		p.status.SetDownloadSuccess()

		if err := p.activate(ctx, u.Bundle); err != nil {
			p.logError("Bundle activation failed: %v", err)
			p.status.SetError(err)
			return
		}

		p.status.SetError(nil)
		p.status.SetActivateSuccess(u.Bundle.Manifest.Revision)
		if u.ETag != "" {
			p.logInfo("Bundle downloaded and activated successfully. Etag updated to %v.", u.ETag)
		} else {
			p.logInfo("Bundle downloaded and activated successfully.")
		}
		p.etag = u.ETag
		return
	}

	if u.ETag == p.etag {
		p.logDebug("Bundle download skipped, server replied with not modified.")
		p.status.SetError(nil)
		return
	}
}

func (p *Plugin) activate(ctx context.Context, b *bundle.Bundle) error {
	p.logDebug("Bundle activation in progress. Opening storage transaction.")

	return storage.Txn(ctx, p.manager.Store, storage.WriteParams, func(txn storage.Transaction) error {
		p.logDebug("Opened storage transaction (%v).", txn.ID())
		defer p.logDebug("Closing storage transaction (%v).", txn.ID())

		// write data from bundle into store, overwritting contents
		if err := p.manager.Store.Write(ctx, txn, storage.AddOp, storage.Path{}, b.Data); err != nil {
			return err
		}

		if err := p.writeManifest(ctx, txn, b.Manifest); err != nil {
			return err
		}

		// load existing policy ids from store and delete
		ids, err := p.manager.Store.ListPolicies(ctx, txn)
		if err != nil {
			return err
		}

		for _, id := range ids {
			if err := p.manager.Store.DeletePolicy(ctx, txn, id); err != nil {
				return err
			}
		}

		// ensure that policies compile.
		modules := map[string]*ast.Module{}

		for _, file := range b.Modules {
			modules[file.Path] = file.Parsed
		}

		compiler := ast.NewCompiler()
		if compiler.Compile(modules); compiler.Failed() {
			return compiler.Errors
		}

		// write policies from bundle into store.
		for _, file := range b.Modules {
			if err := p.manager.Store.UpsertPolicy(ctx, txn, file.Path, file.Raw); err != nil {
				return err
			}
		}

		return nil
	})
}

func (p *Plugin) writeManifest(ctx context.Context, txn storage.Transaction, m bundle.Manifest) error {

	var value interface{} = m

	if err := util.RoundTrip(&value); err != nil {
		return err
	}

	if err := storage.MakeDir(ctx, p.manager.Store, txn, bundlePath); err != nil {
		return err
	}

	return p.manager.Store.Write(ctx, txn, storage.AddOp, manifestPath, value)
}

func (p *Plugin) logError(fmt string, a ...interface{}) {
	logrus.WithFields(p.logrusFields()).Errorf(fmt, a...)
}

func (p *Plugin) logInfo(fmt string, a ...interface{}) {
	logrus.WithFields(p.logrusFields()).Infof(fmt, a...)
}

func (p *Plugin) logDebug(fmt string, a ...interface{}) {
	logrus.WithFields(p.logrusFields()).Debugf(fmt, a...)
}

func (p *Plugin) logrusFields() logrus.Fields {
	return logrus.Fields{
		"plugin": Name,
		"name":   p.config.Name,
	}
}

var (
	bundlePath   = storage.MustParsePath("/system/bundle")
	manifestPath = storage.MustParsePath("/system/bundle/manifest")
)